The invention relates to a plurality of different processes for integrating fasteners into a knitted seat cover and to a seat cover that has fasteners for fastening to a seat cover support. However, the fasteners are also suitable for fastening other textile elements such as insulation and filter inserts.
In the past, fasteners, such as those in the form of tubes or eyes, had to be sewn onto a preassembled seat cover in a separate sewing operation. Since these seat covers generally were woven and always had to be assembled to create a three-dimensional seat cover (in other words, the individual pieces of the seat cover had to be sewn together), sewing the fasteners onto the underside of the seat cover in an additional step generated a relatively insignificant amount of additional work.
Today, it is possible to knit a three-dimensional seat cover without ever having to do any assembling. This means that a technical solution has to be found in which the fasteners can be integrated into the cover when the cover is being knitted.
EP 361 855 A1 discloses a process in which tubular fasteners are knitted on in a single piece during manufacturing, in other words, when the seat cover is being knitted. The advantage of this approach is that the additional process step of sewing the fasteners on at the desired locations is eliminated. However, this process greatly increases machine operating times, and the tubular fasteners, which are also knitted as a tube when the seat cover itself is being knitted, cannot be produced in any desired length or any desired strength. Another disadvantage of this process is that the locations at which the fasteners are knitted on are generally visible on the visible side of the seat cover.
The object of the present invention is therefore to create a process that permits seat covers having integrated fasteners to be manufactured quickly and in which the fasteners exhibit a high degree of stability, can be manufactured in any desired shape and with any desired stability, and are less visible from the visible side of the knitted fabric than is the case in prior-art processes. It is also the object of the invention to create a seat cover having integrated fasteners that are not visible from the visible side and that permit the seat cover to be optimally fit onto the seat cover support.
In the invention, fasteners are integrated into the knitted seat cover while the cover is being manufactured. However, these fasteners are not knitted together with the cover. Instead, they are added as separate parts during manufacturing, and are then knitted into the seat cover. The feeding-in of these parts can be accomplished by means of carriers from which the fasteners are transferred to the needle bed. To accomplish this, the carriers must have areas on which the loops of the premanufactured fasteners are hung. These sections must have spacings corresponding to the gauge of a needle bed on the flat-bed knitting machine. This makes it easy to transfer the fasteners from the carrier onto the needle bed.
Another way to feed the fasteners to the knitted area on the flat-bed knitting machine is as yard goods. In this case, the fasteners can be of various lengths and sizes. The yard goods are then preferably rolled up and fed into the knitting area by means of a special feed system, for example by means of a thread guide with a thread feed mechanism. The thread guide preferably contains a cutting device to cut the yard goods at the desired position. The fasteners are then knitted into the knitted fabric in the manner of a weft thread.
In a further alternative, the fasteners can also be knitted at the same time as the seat cover on a different needle bed of a flat-bed knitting machine and then transferred to the desired position in the knitting area, or simply knitted together, an operation which can be accomplished in particular on four-bed machines. This also avoids increasing the machine run times while the fasteners are being knitted, since in this embodiment of the invention the seat cover and the fasteners are knitted simultaneously on separate needle beds.
Elastic threads or synthetic fibers having good elastic properties can be knitted into the aforesaid fasteners, which may generally be configured as punctiform or linear fasteners, in order to fix the position of the seat cover elastically on the support by means of the fasteners. When various elastic threads are used in this way, the elasticity and recovery properties of the system used to mount the fasteners can be defined precisely. As a general rule, elastic threads or groups of elastic threads that are floated over several needles, or elastic threads or groups of elastic threads that are inserted as loops, warp and/or weft threads can be utilized to make the attachment to a hook that would be embodied in the seat cover support. The fasteners can also be embodied as elastic borders, elastic tapes, elastic loops or elastic tunnels, depending on which fastening method is desired.
The connection between the fasteners that are added and the main knitted fabric of the seat cover may also be produced by thermal means as well as by knitting. For example, the fasteners may be composed of tapes or welts that can have fasteners such as eyes or hooks. The fasteners can also be in the form of tubes that are made thicker using wires or cords to form an elongated thicker area that can be hooked or clipped into receiving areas. A thicker area of this type can be hardened and stabilized by means of a thermal treatment. A thicker area of this type can preferably be knitted directly onto the underside of a tubular cover so that it can be pulled onto a frame. This thicker area is then grasped by complementary fasteners and can be used to connect the ends of the cover or to secure the cover on a frame.
As an alternative to the processes described above, the fastener can also be integrated into the seat cover. In this case, in a first alternative, adhesive threads having a low melting point, for example Grilon(copyright) manufactured by Ems Chemie, can either be knitted together as the main knitted fabric and/or they can be inserted or plaited on as warp or weft threads. The adhesive thread is preferably incorporated in the main knitted fabric in such floated loops, in other words in a very widely spaced loop structure, or it is incorporated into the main knitted fabric in the form of loops similar to terry-cloth loops. Next, the cover is pulled onto the three-dimensional support part. The cover is then bonded onto the cushion support, for example by means of simple steam heating, at the points at which the adhesive thread touches the knitted fabric as well as the support. In the case of warp or weft threads or floated structures, for example, these points can be linear areas or points that provide optimal contact of the cover to the support in a contoured area as a consequence of their carefully selected distribution. This method can be used in particular with foam cushion supports and, as an alternative to or in addition to the aforesaid linear or punctiform fasteners, it can be integrated in the form of loops, welts or tapes knitted onto the seat cover. In addition to the inclusion of adhesive threads, thermal shrink threads can be applied at highly contoured areas, which then contract somewhat with thermal treatment, causing the upholstery cover to lie taut on the seat cushion or seat support. Combining the adhesive thread with the thermal shrink thread, which can be incorporated into the main knitted fabric in the same way as the adhesive thread, achieves an optimal connection between the seat cover and the seat cover support across the surface of the cover and ensures that the cover fits optimally on the support. There are two reasons for this: first, upon thermal treatment the upholstery cover shrinks down snugly onto the upholstery support, and second, the adhesive threads are activated at the same time as the aforesaid shrinking occurs, thus creating a good connection between the seat cover and the seat cover support. This produces seats that have strong visual appeal and a uniform look, and whose fasteners are not visible from the outside. Using adhesive or hot-melt threads to make the attachments means that the cover can be joined directly to the support following the thermal treatment and that no barrier films are needed between the cover and the foam molded onto the support. As a result, seating is comfortable and well ventilated.
As an alternative to or in addition to the attachment technology in which adhesive threads are used to achieve bonding over large surface areas, hook-and-loop tapes or hook-and-loop surfaces can be provided on the side of the seat cover facing the seat cover support. In this case, for example, the looped tapes having the loops can be embodied in the cover by knitting the loops right into the material. However, the hooks of the hook-and-loop fastening structure can also be embodied in the form of loops if said loops are knitted into the support side of the seat cover using a relatively hard, thick monofilament and are then cut open at a defined angle, for example using a blade integrated with the needles on the flat-bed knitting machine. In this way, at least one hook is formed from a loop. This loop can interact with the complementary looped side of the hook-and-loop fastening structure. Thus, both sides of the hook-and-loop connection can be integrated into the seat cover without the need for additional process steps and without significantly increasing the length of time that the machines need to run to produce the seat cover. The loops can also be stabilized in the cover by means of adhesive threads or hot-melt threads.
As an alternative to or in addition to the incorporation of thermal shrink threads as already described above, elastic threads can of course also be integrated into the basic structure of the knitted fabric, so that the seat cover contacts the seat cover support in an elastic manner.